CN101467412A - Signal detection in multicarrier communication system - Google Patents

Abstract

The present invention provides a signal detection mechanism. According to the signal detection mechanism provided, the received signal is correlated with the reference signal in the frequency domain. Thus, the received power of the received signal is calculated and the correlation value is normalized with the received power. Therefore, a single threshold may be used regardless of the reception power of the received signal when comparing the correlation between the received signal and the reference signal with the threshold in order to determine whether the received signal is a desired signal or noise.

Description

Signal Detection in Multi-Carrier Communication Systems

technical field

The present invention relates generally to signal processing implemented in a radio receiver and in particular to signal detection in a radio receiver capable of receiving and processing signals transmitted according to a multi-carrier data transmission mechanism.

Background technique

Multi-carrier data transmission mechanisms have been extensively studied and used to some extent as high-speed wireless data transmission mechanisms between two independent communication devices or in wireless telecommunication systems. Such multi-carrier data transmission schemes include, for example, Orthogonal Frequency Division Multiplexing (OFDM) schemes. In a multicarrier system several data symbols are usually transmitted in parallel on multiple subcarriers. In order to achieve data transmission between a transmitter and a receiver, the receiver must be able to detect a given synchronization or pilot signal transmitted by the transmitter. Synchronization or pilot signals may be attenuated due to fading caused by the radio channel and thus may reach the receiver at a very low power level. Therefore, there is a need for an efficient signal detection method for detecting synchronization signals and/or pilot signals within a multi-carrier signal received in a radio receiver.

Signal detection can be implemented in the time domain or the frequency domain in an OFDM system. Signal detection is generally based on correlations of received signals that are processed for detection. The signal detection process may be blind or pilot assisted. The autocorrelation properties of the received signal, in particular the correlation properties caused by the use of cyclic prefixes, are often used in blind signal detection. In pilot assisted signal detection, a received signal is correlated with a known signal, and if the two signals have sufficient correlation, it is determined that the signal has been detected.

Signal detection is generally based on a comparison of a calculated correlation value of the received signal with a threshold. Since the correlation value is calculated from signal samples having a given received power level, the correlation value is influenced by the received power of the received signal. Therefore, the threshold must be calculated by taking the received power of the received signal into consideration. In practice, thresholds must be calculated for each signal detection process. This increases the amount of signal processing and thus the complexity of the radio receiver implementing the signal detection process.

Contents of the invention

It is an object of the present invention to provide an improved solution for signal detection in radio receivers.

According to an aspect of the present invention, a signal detection method in a radio receiver is provided. The method includes: receiving a first radio signal; transforming the received first radio signal into the frequency domain; selecting one or more specific frequency components of the transformed first radio signal, thereby obtaining A frequency-domain representation of a signal with frequency components; correlating the frequency-domain representation of a signal at one or more selected frequency components with a reference signal, thereby generating a correlation value that describes the The similarity between the signal of each frequency component and the reference signal; estimate the received power value for the signal located at one or more selected frequency components; calculate the decision metric according to the correlation value and the received power value; and determine based on the decision metric Whether the signal at the selected frequency component or components is a desired signal or noise.

According to another aspect of the present invention, a radio receiver is provided. The radio receiver includes: a communication interface configured to receive radio signals; and a processing unit. The processing unit is configured to: receive a first radio signal via a communication interface; transform the received first radio signal into the frequency domain; select one or more specific frequency components of the transformed first radio signal, thereby obtaining A frequency-domain representation of a signal at the selected one or more frequency components; correlating the frequency-domain representation of the signal at the selected one or more frequency components with a reference signal, thereby producing a correlation value that describes Similarity between a signal at the selected one or more frequency components and a reference signal; estimate a received power value for a signal at the selected one or more frequency components; calculate a decision metric based on the correlation value and the received power value ; and determining whether the signal at the selected one or more frequency components is a desired signal or noise based on the decision metric.

According to another aspect of the present invention, a mobile terminal for use in a wireless communication network is provided. The mobile terminal includes a radio receiver configured to: receive a first radio signal; transform the received first radio signal into the frequency domain; select one or more specific components of the transformed first radio signal frequency components, thereby obtaining a frequency domain representation of a signal located at one or more selected frequency components; correlating the frequency domain representation of a signal located at one or more selected frequency components with a reference signal, thereby generating a correlation value, The correlation value describes the similarity between the signal located in the selected one or more frequency components and the reference signal; the received power value is estimated for the signal located in the selected one or more frequency components; according to the correlation value and the received calculating a decision metric based on the power value; and determining whether the signal at the selected one or more frequency components is a desired signal or noise based on the decision metric.

According to another aspect of the present invention there is provided a computer-readable computer program distribution medium encoding computer program instructions for executing a computer process for signaling in a radio receiver detection. The process includes: receiving a first radio signal; transforming the received first radio signal into the frequency domain; selecting one or more specific frequency components of the transformed first radio signal, thereby obtaining A frequency-domain representation of a signal with frequency components; correlating the frequency-domain representation of a signal at one or more selected frequency components with a reference signal, thereby generating a correlation value that describes the The similarity between the signal of each frequency component and the reference signal; estimate the received power value for the signal located at one or more selected frequency components; calculate the decision metric according to the correlation value and the received power value; and determine based on the decision metric Whether the signal at the selected frequency component or components is a desired signal or noise.

The present invention provides several advantages. The invention enables a more robust detection of a signal that has been transmitted on a given subcarrier simultaneously with one or more other signals transmitted on other subcarriers. Furthermore, the invention enables simplified signal detection regardless of the received power level of the signal being processed for detection.

Description of drawings

Hereinafter, the present invention will be described in more detail with reference to embodiments and accompanying drawings, in which:

Figure 1 illustrates a block diagram of an example communication system in which embodiments of the present invention may be implemented;

Figure 2 illustrates an example of the frequency spectrum of a multi-carrier signal received in a radio receiver according to one embodiment of the invention;

Figure 3 illustrates signal detection implemented in radio reception according to one embodiment of the invention;

Figure 4 illustrates signal detection implemented in a radio receiver according to another embodiment of the invention;

Figure 5 illustrates signal detection implemented in a radio receiver according to yet another embodiment of the present invention; and

FIG. 6 is a flowchart illustrating a signal detection process according to one embodiment of the present invention.

Detailed ways

Referring to Figure 1, an example of a communication system to which embodiments of the present invention may be applied is examined. The communication system may be a mobile communication system such as Universal Mobile Telecommunications System (UMTS), Wireless Local Area Network (WLAN), or the like. Alternatively, the communication system may comprise two independent communication devices, such as two mobile phones, in wireless communication with each other. Communication systems may utilize multi-carrier data transmission mechanisms such as Orthogonal Frequency Division Multiplexing (OFDM).

Referring to FIG. 1 , an example of the structure of a radio receiver 100 to which the embodiment of the present invention can be applied will be considered. The radio receiver 100 in FIG. 1 is a radio receiver 100 capable of wireless communication and capable of at least receiving information transmitted over a radio channel. The radio receiver 100 may be capable of receiving information transmitted according to OFDM technology. The radio receiver 100 may eg be a personal mobile communication or information processing device, such as a computer, a PDA (Personal Digital Assistant) or a mobile terminal of a wireless communication system. The radio receiver 100 can also be a unit of a communication network, such as a base station of a mobile communication system or an access point to a WLAN. In addition, a radio receiver may be a component in an electronic device that receives and processes radio signals according to an embodiment of the present invention.

The radio receiver 100 comprises a communication interface 108 for receiving information transmitted over a radio channel. The communication interface 108 may be a receiving unit configured to receive information transmitted using any of the communication techniques described above. Communication interface 108 may be configured to process received information signals to some extent. Communication interface 108 may be configured to filter and amplify received information signals and to convert analog information signals to digital form. In addition to receiving information signals, communication interface 108 may be configured to transmit information signals over a radio channel.

The radio receiver 100 also includes a processing unit 104 configured to control the operation of the radio receiver 100 . The processing unit 104 may be configured to process information received via the communication interface 108 . In particular, the processing unit 104 may be configured to perform digital signal processing algorithms on received information in order to reliably detect transmitted information signals. The processing unit 104 may be implemented with a digital signal processor with appropriate software embedded on a computer readable medium, or with discrete logic circuits, for example with an ASIC (Application Specific Integrated Circuit).

The radio receiver 100 may also include a memory unit 106 for storing information. Memory unit 106 may be any type of non-volatile memory. The memory unit 106 may store software necessary for the operation of the radio receiver, and also specific parameters necessary for the reception and processing of radio signals.

The radio receiver 100 may also include a user interface 102 for interaction between the radio receiver and a user of the radio receiver 100 . User interface 102 may include input devices such as a keyboard or keypad, a display device, a microphone, and speakers.

The radio receiver 100 may have a connection to a radio transmitter 110 comprising a communication interface 114 and a processing unit 112 . The radio transmitter 110 may have the capability to transmit information according to OFDM techniques, ie to transmit multi-carrier OFDM signals.

Next, signal detection implemented in the radio receiver 100 according to one embodiment of the present invention will be described with reference to FIGS. 2 to 5 .

FIG. 2 illustrates an example of a frequency domain representation of an OFDM signal that may be received in the radio receiver 100 . As known in the art, an OFDM signal is a multicarrier signal comprising multiple subcarriers centered at different frequencies. As shown in Figure 2, the frequency spectrum of the subcarriers may overlap. According to the OFDM transmission technique, data is transmitted on multiple subcarriers during an OFDM symbol interval. A given signal may be transmitted on every subcarrier of a multicarrier OFDM signal or only on given subcarriers, for example every Nth subcarrier. According to the latter mechanism, subcarriers of a multi-carrier OFDM signal can be allocated to multiple different signals in an OFDM symbol interval. In Fig. 2, subcarriers of a multi-carrier OFDM signal have been allocated to three signals S1, S2 and S3. Signal S1 is located on subcarriers centered on frequencies f1, f4 and f7, signal S2 is located on subcarriers centered on frequencies f2, f5 and f8, and signal S3 is located on subcarriers centered on frequencies f3 and f6. One of the signals S1 , S2 and S3 may be a desired signal that the radio receiver 100 is trying to detect, eg for synchronization purposes. Thus, the desired signal may eg be a synchronization signal or a pilot signal. In order to realize the data transmission between the transmitter and the receiver, the receiver must detect the signal transmitted by the transmitter. When a signal transmitted by the transmitter, such as a synchronization signal, has been detected, the receiver activates other processes required for data reception. Such a process may eg include synchronization with a synchronization signal.

The performance of the signal detection mechanism can be determined in terms of the number of correct signal detections versus false alarms. A false alarm means that other signals such as noise have been detected as the desired signal (eg synchronization signal). In such a situation, the receiver tries to synchronize with the wrong signal or even with noise, which causes unnecessary operation in the receiver. As mentioned above, signal detection is generally based on a comparison of a correlation property of the received signal with a threshold. Based on the comparison, the received signal is determined to be a desired signal or noise. The threshold should be set such that the signal detector on the one hand is able to detect even weak signals and on the other hand minimizes false alarms, even detection of noise as the desired signal. In order to reduce the computational complexity of signal detection algorithms in radio receivers, a common threshold that can be used regardless of the received power of the received signal would be advantageous.

Figure 3 illustrates a signal detection mechanism according to one embodiment of the present invention. Radio signals are received in a radio receiver, such as radio receiver 100 . The received radio signal may be a multi-carrier OFDM radio signal having the structure shown in Fig. 2 or it may be noise. The radio receiver 100 does not know this, so it performs a signal detection process. The radio receiver 100 processes the received radio signal as if it were a multi-carrier OFDM signal. Thus, different signals in a multicarrier OFDM signal will be allocated to different subcarriers of the multicarrier signal. Radio signals received by the antenna of the radio receiver 10 are first filtered, amplified and converted to baseband (not shown). The received radio signal is then converted from analog to digital in the A/D converter 300 . The digitized radio signal is then transformed into the frequency domain by means of a Fourier transform in a Fourier transformer 302, thereby producing a frequency domain representation of the received radio signal. The Fourier transform may be performed by utilizing a Fast Fourier (FFT) algorithm.

The frequency domain representation of the received radio signal is then fed to a subcarrier selector 304, which selects a signal on one or more specific frequency components or subcarriers of the received radio signal. Signals at one or more specific frequency components are selected for signal detection. The subcarrier selector 304 may eg select those frequency components known to contain subcarriers carrying synchronization signals or pilot signals. Returning to Fig. 2, assume that the radio receiver attempts to detect the synchronization signal S1. Thus, the subcarrier selector 304 selects the frequency components whose center frequencies are f1, f4 and f7 and whose bandwidth corresponds to the known OFDM subcarrier bandwidth. Thus, the radio receiver obtains a signal S having frequency components f1, f4 and f7. Subcarrier selector 304 may select desired frequency components, eg, by filtering out unwanted frequency components. It should be noted that the radio receiver can know which component or components should be checked in order to detect the synchronization signal.

The signal S at the selected frequency component is fed from the subcarrier selector 304 to a correlator 308 and a power estimator 306 . The correlator 308 correlates the signal received from the subcarrier selector 304 with the reference signal to calculate a correlation value. The reference signal may be pre-stored in the memory unit 106 of the radio receiver 100 . If the signal received from the subcarrier selector is S(n) and the reference signal is SR(n), where both include N (n=1 to N) samples, then the correlation value can be calculated according to the following equation:

$\mathrm{<span\; class="notranslate">\; C</span>}<span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; N</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}\mathrm{<span\; class="notranslate">\; S</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; SR</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

Sample n may be a frequency domain sample of signals S and SR. Thus, the frequency domain representation of the signal S is related to the frequency domain representation of the reference signal SR. The correlator 308 then outputs a correlation value C. It should be noted at this stage that the radio receiver 100 knows the waveform of the transmitted synchronization signal it is trying to detect and that the reference signal has a corresponding waveform. In the ideal case, S(n)=SR(n) when the received signal is actually the signal that the radio receiver is trying to detect. If the radio receiver 100 does not know the phase of the received signal S(n), the correlator 100 can calculate equation (1) with different time shifts between the signal S(n) and SR(n) and choose the largest value. The correlator 308 may be of the type known as a sliding correlator.

The power estimator 306 estimates the received power of the signal S received from the subcarrier selector 304, that is, the received power of the signal S on the selected frequency components f1, f4 and f7. The power estimator 306 can calculate the received power value P according to the following formula:

$\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; N</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}{<span\; class="notranslate">\; |</span>\mathrm{<span\; class="notranslate">\; S</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; |</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

The power estimator 306 then outputs the calculated received power value of the signal at the selected frequency component.

The divider 310 receives the correlation value C from the correlator 308 and the received power value P from the power estimator 306 . The divider 310 divides the correlation value C by the received power value P, thereby normalizing the power of the correlation value C and thus canceling the influence of the received power on the correlation value C. As a result, the divider 310 outputs a decision metric that feeds a comparator 312 . A comparator 312 compares the decision metric with a threshold in order to determine whether the received signal S has a sufficient correlation with the reference signal SR. The threshold value may be pre-stored in the memory unit 106 . If the decision metric is above the threshold, the comparator 312 determines whether the received signal S is the desired signal (synchronization signal S1). Thus, the comparator may output a signal that activates a synchronization process in the radio receiver 100 such that the radio receiver 100 may start to synchronize itself to the synchronization signal. On the other hand, if the decision metric is below the threshold, the comparator 312 determines that the received signal S is noise. Accordingly, the comparator 312 may output a signal indicating that the desired signal is not found in the received signals.

The power normalization implemented by divider 310 in conjunction with power estimator 306 simplifies the signal detection process such that the same fixed threshold can be applied regardless of the received power of the received signal. There is therefore no need to calculate thresholds separately for each signal detection process. This significantly simplifies the signal detection process.

In the embodiment described above with reference to FIG. 3 , the correlation process and the received power estimation process are calculated for signals located at a plurality of frequency components as well. This means that multiple frequency components have been jointly processed. As mentioned above, each subcarrier (frequency component) of the signal S1 that the radio receiver 100 tries to detect carries one symbol during the OFDM symbol interval. Thus, signal S1 on subcarriers centered at f1, f4 and f7 carries three symbols during the OFDM symbol interval. Therefore, signal S1 is the sum of three symbols. Thus, the reference signal SR used in the correlation process may be the sum of three corresponding symbols.

Fig. 4 illustrates another embodiment of the invention, where the frequency components selected by the subcarrier selector 304 are processed in the correlator 400 and in the power estimator 402, respectively. The correlator 400 correlates the signals on each selected frequency component with the corresponding reference signal, thereby generating as many correlation values as the number of selected frequency components. It is also assumed that the subcarrier selector 304 has selected the signal S on frequency components whose center frequencies are f1, f4 and f7. According to this embodiment of the invention, the signal S is divided into signals S1 , S2 and S3 each associated with a frequency component having center frequencies f1 , f4 and f7 respectively. The correlator 400 then correlates each signal S1, S2 and S3 with a corresponding reference signal SR1, SR2 and SR3, respectively. Correlation can be achieved according to equation (1). For example, signal S1 is correlated with a reference signal representing a signal known to be transmitted on a subcarrier centered at frequency fl. Accordingly, the correlator 400 outputs correlation values C1, C4, C7 associated with the signals S1, S2 and S3, respectively.

Similarly, the power estimator 402 estimates the received power of the signal S for each frequency component, ie for the signals S1, S2 and S3 respectively. Received power estimation can be implemented according to equation (2). Thus, the power estimator 302 outputs relative power values P1, P4, P7 for the signals S1, S2 and S3, respectively.

The correlation values C1, C4 and C7 and the received power values P1, P4 and P7 are fed to a combiner 404 which combines the correlation values C1, C4 and C7 and the received power values P1, P4 and P7 to produce one correlation value C and a received power value P. The combiner 404 may simply be a summer summing the correlation values C1, C4 and C7 together. Combiner 404 may sum received power values P1, P4, and P7 together in a similar manner. The correlation value C and the received power value are then fed to a divider 310 to generate a decision metric used to enable the determination of whether the received signal is the desired signal S1 or noise.

Figure 5 illustrates yet another embodiment of the present invention. If the same signal that the radio receiver 100 is trying to detect is transmitted in diversity, eg several transmissions, the radio receiver 100 can improve the accuracy of the decision metric by averaging. The subcarrier selector 304 also selects frequency components known to contain the desired signal (synchronization signal). Thus, the subcarrier selector 304 can select the same frequency component for a newly received radio signal as the frequency component selected for a previously received radio signal. On the other hand, the subcarrier selector 304 may select a different frequency component for a newly received radio signal than a frequency component selected for a previously received radio signal. For example, different frequency components at different times can be used in order to take advantage of frequency diversity, thereby improving the performance of the signal detection process. A plurality of decision metrics, each associated with a different received radio signal, may be calculated according to any of the methods described above and input from the divider 310 to the averaging unit 500 . The averaging unit 500 may then calculate an average decision metric by averaging a plurality of received decision metrics. Averaging multiple decision metrics improves the performance of the signal detection mechanism. For example, if the previously transmitted synchronization signal was weak due to severe fading in the radio channel, the received synchronization signal may not correlate sufficiently with the reference signal to be detected. But if the same sync signal transmitted subsequently is not affected by severe fading, this received sync signal correlates well with the reference signal and can, after averaging, raise the decision metric above the threshold level to detect the sync signal.

Next, a signal detection process implemented in a radio receiver according to one embodiment of the present invention will be described with reference to the flowchart in FIG. 6 . The process begins in block 600 .

In block 602, a radio signal is received in a radio receiver. The received radio signal is transformed into the frequency domain by FFT in block 604, thereby obtaining a frequency domain representation of the received radio signal. One or more specific frequency components of the received and transformed radio signal are selected in block 606 . If a radio receiver attempts to detect a signal that is known to be transmitted on multiple subcarriers of a multicarrier signal, such as an OFDM signal, then the frequency component corresponding to the subcarrier carrying the desired signal is selected.

In block 608, the signal on the selected frequency component is compared to the reference signal, thereby obtaining a correlation value describing the similarity between the signal on the selected frequency component and the reference signal. Correlation may be achieved by correlating a single signal comprising selected frequency components with a corresponding reference signal. Optionally, the correlation may be implemented by correlating each frequency component with a reference signal of the same frequency component respectively. In the former case one correlation value is obtained, while in the latter case a plurality of correlation values are obtained. Multiple relevance values may be combined according to a specific combination mechanism.

In block 610, received power values are calculated for the selected frequency components. Also, the received power may be calculated by calculating the power of a signal representing each selected frequency component, or the received power may be calculated for each frequency component separately. In the latter case, the received power values of the frequency components may be combined according to a specific combination mechanism.

Based on the correlation value calculated in block 608 and the received power value of the selected frequency component calculated in block 610, a decision metric is calculated in block 612. The decision metric may be calculated by dividing the correlation value by the received power value, thereby normalizing the power of the correlation value, ie removing the influence of received power from the correlation value.

In block 614, it is determined whether another decision metric is to be calculated. If the radio receiver knows that a desired signal that the radio receiver is trying to detect is transmitted multiple times, the radio receiver may choose to take advantage of this diversity transmission in order to improve the accuracy of the decision metric. If it is determined in block 614 that another metric is to be calculated, then the process returns to block 602 . If in block 614 it is determined that another decision metric is not to be calculated, the process proceeds to block 616 where an average of the calculated decision metrics is calculated. If only a single decision metric has been calculated, block 616 need not be performed.

The process then proceeds to block 618, where the decision metric (or the average of the decision metric) is compared to a threshold. If the decision metric is above the threshold, the process proceeds to block 622 where it is determined that the received signal is the desired signal. On the other hand, if the decision metric is below the threshold, the process proceeds to block 620 where it is determined that the received signal is noise. The process ends in block 624 .

Embodiments of the invention may be implemented in a radio receiver comprising a communication interface and the processing unit 104 operatively connected to the communication interface 108 . The processing unit 104 may be configured to perform at least some of the steps described in connection with the flowchart of FIG. 6 and in connection with FIGS. 3-5 . An embodiment may be implemented as a computer program comprising instructions for executing a computer process for signal detection in a radio receiver.

The computer program can be stored on a computer program distribution medium readable by a computer or a processor. A computer program medium may be, for example but not limited to, an electronic, magnetic, optical, infrared or semiconductor system, device or transmission medium. The computer program medium may include at least one of the following: computer readable medium, program storage medium, recording medium, computer readable memory, random access memory, erasable programmable memory, computer readable software distribution package, Computer readable signals, computer readable telecommunication signals, computer readable printed matter and computer readable compressed software packages.

Although the invention has been described above with reference to examples according to the accompanying drawings, it is self-evident that the invention is not restricted thereto but that it can be modified in several ways within the scope of the appended claims.

Claims (24)

1. A method of signal detection in a radio receiver, said method comprising: receiving a first radio signal; transforming said received first radio signal into a frequency domain; selecting one or more specific frequency components of said transformed first radio signal, thereby obtaining a frequency domain representation of the signal at the selected one or more frequency components; correlating said frequency domain representation of said signal at the selected one or more frequency components with a reference signal, thereby generating a correlation value describing said frequency domain representation at the selected one or more frequency components the similarity between the signal and the reference signal; estimating a received power value for said signal at the selected one or more frequency components; computing a decision metric from said correlation value and said received power value; and Whether the signal at the selected one or more frequency components is a desired signal or noise is determined based on the decision metric. 2. The method of claim 1, wherein the decision metric is calculated by dividing the correlation value by the received power value. 3. The method according to claim 1 , wherein said decision metric is achieved by comparing said decision metric with a fixed threshold and deciding whether said signal at a selected one or more frequency components is a desired signal or noise based on said comparison. Said to confirm. 4. The method according to claim 3, wherein if the decision metric is higher than the threshold, the signal located at the selected one or more frequency components is determined to be a desired signal, and if the decision metric Below the threshold, the signal at the selected one or more frequency components is determined to be noise. 5. The method of claim 1, wherein the frequency domain representation of the signal at the selected one or more frequency components is correlated with the frequency domain representation of the reference signal. 6. The method according to claim 5, wherein a plurality of frequency components are selected, and the correlation, the received power estimation and the decision metric calculation are respectively implemented for each frequency component, thereby obtaining a plurality of decision metrics, and The method also includes combining the plurality of decision metrics. 7. The method according to claim 1 , wherein a plurality of frequency components are selected, and the correlation, the received power estimation and the decision metric calculation are realized for each frequency component respectively, thereby obtaining a plurality of decision metrics, and The method also includes combining the plurality of decision metrics. 8. The method of claim 1, further comprising: receive at least one other radio signal; performing the same frequency component selection, correlation, received power estimation and decision metric computation operations for said at least one other radio signal as for said received first radio signal, thereby obtaining a plurality of decision metrics; and An average value is calculated for the plurality of decision metrics. 9. The method of claim 8, wherein one or more frequency components are selected for the received at least one other radio signal that are at least partially different from the frequency components selected for the first radio signal. 10. The method of claim 1, wherein the radio receiver is configured to receive multi-carrier radio signals. 11. A radio receiver comprising: a communication interface configured to receive radio signals, and A processing unit configured to: receive a first radio signal via the communication interface; transform the received first radio signal into a frequency domain; select one or more specific frequencies of the transformed first radio signal component, thereby obtaining a frequency-domain representation of the signal at the selected one or more frequency components; correlating the frequency-domain representation of the signal at the selected one or more frequency components with a reference signal, thereby generating a correlation A degree value describing the similarity between the signal at the selected one or more frequency components and the reference signal; estimating reception for the signal at the selected one or more frequency components calculating a decision metric according to the correlation value and the received power value; and determining whether the signal at the selected one or more frequency components is a desired signal or noise based on the decision metric. 12. The radio receiver of claim 11, wherein the processing unit is further configured to calculate the decision metric by dividing the correlation value by the received power value. 13. The radio receiver according to claim 11 , wherein the processing unit is further configured to determine the frequency at the selected one or more frequency components by comparing the decision metric with a threshold and based on the comparison. The determination is made whether the signal is a desired signal or noise. 14. The radio receiver according to claim 13 , wherein the processing unit is further configured to determine the signal at the selected one or more frequency components as determining the desired signal, and determining the signal at the selected one or more frequency components as noise if the decision metric is below the threshold. 15. The radio receiver of claim 11, wherein the processing unit is further configured to receive multi-carrier radio signals via the communication interface. 16. The radio receiver according to claim 11 , wherein the processing unit is further configured to combine the frequency domain representation of the signal at the selected one or more frequency components with the frequency domain representation of the reference signal relevant. 17. The radio receiver according to claim 16 , wherein the processing unit is configured to: select a plurality of frequency components, and implement the correlation, the received power estimation and the decision metric for each frequency component respectively computing, thereby obtaining a plurality of decision metrics; and combining the plurality of decision metrics. 18. The radio receiver according to claim 11 , wherein the processing unit is further configured to: select a plurality of frequency components, and implement the correlation, the received power estimation and the decision for each frequency component respectively metric computation, whereby a plurality of decision metrics are obtained; and combining the plurality of decision metrics. 19. The radio receiver according to claim 11 , wherein the processing unit is further configured to: receive at least one other radio signal through the communication interface; The same frequency component selection, correlation, received power estimation, and decision metric calculation operations are performed on the first radio signal, thereby obtaining a plurality of decision metrics; and calculating an average value for the plurality of decision metrics. 20. The radio receiver according to claim 19, wherein the processing unit is further configured to select for the received at least one other radio signal a frequency component at least partly different from the frequency component selected for the first radio signal. One or more frequency components. 21. A mobile terminal for use in a wireless communication network, said mobile terminal comprising a radio receiver configured to: receive a first radio signal; transmit said received first radio signal transforming into the frequency domain; selecting one or more specific frequency components of said transformed first radio signal, thereby obtaining a frequency domain representation of a signal located at the selected one or more frequency components; said frequency domain representation of said signal at a plurality of frequency components is correlated with a reference signal, thereby yielding a correlation value describing the relationship between said signal at a selected one or more frequency components and said reference signal. a degree of similarity between signals; estimating a received power value for the signal located at the selected one or more frequency components; calculating a decision metric based on the correlation value and the received power value; and determining a decision metric based on the decision metric A determination is made as to whether the signal at the selected one or more frequency components is a desired signal or noise. 22. A radio receiver comprising: means for receiving a first radio signal; means for transforming said received first radio signal into a frequency domain; means for selecting one or more specific frequency components of said transformed first radio signal, thereby obtaining a frequency domain representation of the signal at the selected one or more frequency components; means for correlating said frequency domain representation of said signal at a selected one or more frequency components with a reference signal, thereby generating a correlation value describing a frequency domain at a selected one or more frequency components The similarity between the signal of frequency components and the reference signal; means for estimating a received power value for said signal at a selected one or more frequency components; means for computing a decision metric from said correlation value and said received power value; and means for determining whether the signal at the selected one or more frequency components is a desired signal or noise based on the decision metric. 23. A computer readable computer program distribution medium encoding computer program instructions for executing a computer process for signal detection in a radio receiver, the process comprising: receiving a first radio signal; transforming said received first radio signal into a frequency domain; selecting one or more specific frequency components of said transformed first radio signal, thereby obtaining a frequency domain representation of the signal at the selected one or more frequency components; correlating said frequency domain representation of said signal at the selected one or more frequency components with a reference signal, thereby generating a correlation value describing said frequency domain representation at the selected one or more frequency components the similarity between the signal and the reference signal; estimating a received power value for said signal at the selected one or more frequency components; computing a decision metric from said correlation value and said received power value; and Whether the signal at the selected one or more frequency components is a desired signal or noise is determined based on the decision metric. 24. The computer program distribution medium of claim 23, said distribution medium comprising at least one of the following: a computer readable medium, a program storage medium, a recording medium, a computer readable memory, a computer readable software distribution package , computer readable signals, computer readable telecommunications signals and computer readable compressed software packages.

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